Tag: engines

So today, we are talking about trains. Isn’t it fascinating to watch a single locomotive pulling dozens of wagons at such incredible speed! I remember when I was a kid, I used to sit on the railway platforms waiting for a fast train to pass by & enjoy the loud sounds of locomotives & gust of wind. Ah, those were the days! Anyway, let’s know why do some trains have multiple engines or to be precise why trains have locomotives at the rear end, because that’s what you came here for.

Well, answering the first question is simple. If the train carries more load, a second locomotive is attached. But does it really matter if it is attached to to front or rear part?Yes, it does!

Such a system where a second or other multiple prime movers are coupled at the rear end and/or distributed along the hole train is called distributed power systems. All the commuter, metro & modern electric trains- are a great example of DP systems where motors are located on both the ends as well as at the centre of trains.

Extra power and locomotives are needed generally for freight trains due to heavy load and seldom for passenger trains. But the question springs up again, why rear end? Well, there are number of reasons for this and lets get to them.

The reason why trains have locomotives at the rear end are –

1. Better power delivery

Imagine a case where a freight train runs up a slope. Very high torque is needed to move the whole train because of slope & heavy load. This high torque can result into the front part of locomotive to pivot around rear wheels. The best example you could imagine is lift of the front part of a muscle car or a rider doing a wheelie when one suddenly accelerates(high torque). In case of trains, the engine won’t lift and lose contact with the rails since it’s so heavy but surely it would reduce the normal reaction which results in lower friction. And low friction leads to low power delivery.

An illustration depicting the problem of pivoting.

Consider another case where a locomotive is attached to the last wagon. The problem of pivoting is eliminated significantly since the rear engine is already pushing the cars forward. Along with that, the vertical component of the weight of all the wagons holds down the front part of rear engine developing more friction. Note that the problem of pivoting would reduce but still exist if both engines were located in the front.

2. Lesser chance of joint failure

The engine & wagons are coupled by a combination of hook & knuckle joint(India). If the locomotive pulls the whole train on a up slope, the joint on the head end has to take all the load. This makes the joint vulnerable to drawbar & knuckle pin failures. The attachment of rear engine reduces the chances of failure since it pushes the whole train and reduces the stress.

Here’s a drawing explaining how the rear locomotive helps in reducing amount of stress.

Also while descending, the joint on the tail end carries the all load. This way the location of heavy load region keeps on alternating and ensures that not only one part is subjected to high stresses & thereby reduces number of part failures.

3. Safety

Imagine a freight train powered by 2 locomotives in the front. If due to any reason while climbing a terrain, the coupling between any 2 coaches break, the part which isn’t pulled by the engine becomes a “dead weight“. The train then starts to slide down in the opposite direction possessing very high momentum and this could lead to a disaster! 🙁 The rear & front, both the parts of the train would be in control if the rear end was attached with a locomotive instead of the front end. So this is one of the many advantages of connecting the engine to rear end – Safety!

4. Better acceleration and starting efficiency

Now this… kind of blew my mind. When a train stops at a station, all the slack between the couplings is taken out & the tension between the drawbars of the wagons stay as it is. This means that if the engine starts moving forward, it will have to move the entire train at once. This is similar to a scenario where one tries to expand an already expanded spring.

It will take tremendous amount of power and force to overcome friction and inertia of the whole train at once. So the trick here is that the rear locomotive pushes all the wagons from behind in order to compress all the couplings and letting them slack. Now when the engine starts moving forward carrying the load of one wagon at a time. This method enables the train to consume less energy/fuel to set itself in motion. In passenger trains or trains consisting only 1 locomotive at the front, this is done by reversing the direction of the power.

Fact for the day –

You can connect as many engines as you want in the front or the rear end but they all can be controlled by the motorman/railroad engineer sitting in the frontmost cabin !

Well, if you found this interesting I’m sure you will find my next article more interesting – How do trains turn ? Because they can’t be steered like cars 😛

Just leave everything aside & have a look at these sophisticated & elegant furniture made by a Calfornian company named – MotoArt, which takes furniture to a whole new level of innovation. MotoArt is a company which makes furniture by recycling old parts of military & commercial airplanes. All our home furniture are ordinarily made up of wood, glass or plastic & you can buy them by getting huge discounts through Pepperfry Coupons unlike these amazing stuff… because great things come at a great price !

About MotoArt :-

MotoArt was founded by Donovan Fell & Dave Hall in 2001. When Donovan Fell saw some old dented B-17 propellers in the back of metal scrap pile, he came up with an idea. He gave it some time polishing and degreasing it & made a splendid sculpture. Later on he came to know a place where the old & retired airplanes are sent to. Separating the parts by cutting them they started making cutting edge furniture. Eventually, making high end furniture became their hobby & they made a team as intense labor was needed for separating the parts. Thus evolved the company MotoArt & now as the most recognizable company for making hand crafted high quality corporate and high end furniture from vintage airplane parts.

Their furniture include beds, tables, conference tables, cowling desks, coffee tables, credenzas, couches, chairs, sculptures & my God what not ! If you want to buy furniture from other websites apart from MotoArt’s, you can get great coupons at CouponCanny.in

We have over 100 designs and have produced thousands of pieces that you find nearly in all parts of the world, from the Dubai Burj, to the Sears Tower, and even as far away as the North Pole.

says Dave Hall, the founder & the managing partner of MotoArt.

This proves that there isn’t a shortage of aviation enthusiast in the world 🙂 . Very few are lucky enough to make & work in the field of airplanes or even to relate their name with the modern aviation world(it would be a honour, seriously).

I wonder whether the top Aerospace Companies like Boeing, Airbus Lockheed Martin & many others be using the Cowling reception desk or the long wing/flap conference tables during their meetings & conferences. I wish I could own at least one of those… Damn, my poor ass 🙁 !

Well, my favorite one is the DeskClock?… which one did you like the most ? Share your thoughts in the comment section below. I would love to hear from you 🙂

Rotary/gnome engines were used to power aircrafts during WW-I & radial engines during WW-II. Then came the era of jet engines which completely revolutionized the aviation technology ! Jet engines were very much efficient & powerful than those used during World wars ! The power jet engines deliver is so high that an airplane weighing hundreds of tons lifts off the ground with such ease. How are they capable of producing so much of power/thrust ? So lets not waste our time & have a look on how do jet engines work ?more “How do Gas turbines/Jet propulsion engines work ?”

In my previous article, we learned how 4 stroke engines work ! This time we will learn about the second type of engine i.e 2 stroke engine. The 2 stroke engine is a type of Internal combustion engine where one power cycle is completed with two strokes of the piston during only one rotation of crankshaft. The first commercial two-stroke engine involving in-cylinder compression is attributed to Scottish engineer Dugald Clerk.

The 2 stroke engine performs all the same steps which are performed by 4 stroke engine – suction, compression, expansion & exhaust; but the 2 stroke engine performs these all steps in only 2 stroke unlike the 4 stroke engine which completes one power cycle in 4 strokes. more “How does a 2 stroke engine work ?”

These are the most basic engines used in cars & bikes i.e Four stroke cycle petrol engine OR 4 stroke engine(often called). It is very easy to understand until & unless you wanna do all the thermodynamic calculations & all that stuff ! more “How does a 4 stroke engine work ?”

Imagine you are on-board a ship & what would be the worst thing that would happen to you ? – the water flooding inside the ship making it sink to the seabed…damn…! So we need something which ensures either it doesn’t sink OR even after sinking, all be safe. So in simple words – a Submarine is a vehicle which allows us to travel on water as well as deep inside the seas & oceans. Also a submarine is used in military for protection purposes. more “How does a submarine work ?”

NASA has performed a nearly 9 minute long test of the engine called RS-25 which will be used for next generation mega-rockets which will take the astronauts to Mars & other deep space missions.

The agency successfully tested an RS-25 engine at Stennis Space Center in Mississippi. A total of four RS-25 engines will be used to power the SLS rocket (Space Launch System).

The engine was tested for 535 seconds, which is the same amount of time the engines will fire uring actual SLS launch.

The test was the sixth of seven planned hot-fire trials for the RS-25, which also served as the main engine for NASA’s now-retired space shuttle fleet, ‘Space.com’ reported. The seven-test series is “designed to put the upgraded former space shuttle main engines through the rigorous temperature and pressure conditions they will experience during a launch,” NASA officials said.

“The tests also support the development of a new controller, or ‘brain,’for the engine, which monitors engine status and communicates between the vehicle and the engine, relaying commands to the engine and transmitting data back to the vehicle,” the officials added.

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About MechStuff :-

MechStuff is a blog for people who have passion for learning mechanics, mechanical principles, mechanisms & science behind machines/vehicles. In other words, it is for them who get an adrenaline rush when they hear the sounds of super sport cars, jet engines, locomotives & what not !!! :D